A wireless local area network (WLAN) is a digital communications network that allows a wireless network device to communicate with or access a computer network via a radio communication link. A common type of WLAN is known as “WiFi” or “802.11,” the latter term in reference to the IEEE 802.11 set of standards that govern such networks. Such an 802.11 WLAN commonly comprises one or more access points (APs) that are each connected by a wired connection with a switch, router or similar networking device. Each AP includes an AP radio, an AP antenna, and AP control circuitry. The AP control circuitry commonly includes an Ethernet interface for forming the wired connection with the networking device. The networking device allows a wireless client device, such as a portable computer, smartphone, etc., to communicate with or access a computer network. It is common for the networking device to provide the wireless client device with a connection to the Internet.
A system in which AP antennas are located remotely from the corresponding AP radios may be referred to as a distributed antenna system (DAS). For example, as illustrated in FIG. 1, a DAS 10 may be installed in a building 11, such as an office building or hotel. The antennas 12, 14, 16, 18, etc., are distributed about the various rooms 20, 22, 24, etc., or other spatial regions of building 11, while the corresponding enclosures 26, 28, 30, 32, etc., which house the radio and control circuitry are installed in a centralized location, such as a wiring closet in a basement of building 11. Each such enclosure 26, 28, 30, 32, etc., houses the radio and control circuitry associated with one AP. In a large office building or hotel, dozens of such enclosures may be mounted in a rack or on a wall in the centralized location. In the example shown in FIG. 1, each of enclosures 26, 28, 30, 32, etc., is connected with a respective one of antennas 12, 14, 16, 18, etc., by one of a number of antenna cables 34, 36, 38, 40, etc., and connected with a network switch 42 by one of a number of Ethernet cables 44, 46, 48, 50, etc.
A DAS may carry not only 802.11 WLAN signals but also cellular telephone signals, reflecting a trend of convergence between these two wireless communications technologies. Each AP of such a DAS may include filter circuitry that splits the cellular telephone signals from the 802.11 WLAN signals.
The IEEE 802.11b/g standard defines 14 channels (though only 11 of those channels are commonly used in commercially available WLAN devices in the United States). One common scheme uses a channel set consisting of channels designated by the numbers “1,” “6” and “11,” while another common scheme uses a channel set consisting of channels designated by the numbers “1,” “6,” “11” and “14.” In these schemes, channels “1,” “6,” “11” and “14” represent adjacent, non-overlapping channels or sections of the frequency spectrum.
It is desirable to assign channels to the APs using a scheme that minimizes the likelihood of interference between the signals carried by adjacent antennas. In the example shown in FIG. 1, the APs having adjacent antennas 12 and 14, which are characterized by coverage areas 52 and 54, respectively, would be assigned different channels from each other. For example, the AP having antenna 12 could be assigned channel “1,” while the AP having antenna 14 could be assigned channel “6.” Similarly, the AP having antenna 12 and the AP having antenna 16, which is characterized by a coverage area 56, would be assigned different channels from each other. So, for example, the AP having antenna 16 could be assigned channel “11.” Likewise, the AP having antenna 14 and the AP having antenna 18, which is characterized by a coverage area 58, would be assigned different channels from each other. Algorithms are known that can aid in determining which channels to assign to which APs to minimize the likelihood of interference between signals carried by adjacent antennas.